1. Field of the Invention
This invention relates to a sheet feeding apparatus, an image scanning apparatus and an image forming apparatus provided with the image scanning apparatus, and particularly to a stopper member for abutting against a sheet placed on a sheet stacking tray and blocking the entry of the sheet into a separating part.
2. Description of Related Art
Some of conventional image reading apparatuses such as copying machines and facsimile apparatuses are provided with a document feeding apparatus for feeding documents (originals) placed on a document (original) stacking standby document feeding means, and thereafter separating them one by one by a separating part and feeding them to an image scanning part. As such a document feeding apparatus, there is, for example, one having a sheet feeding apparatus provided with document feeding means for feeding documents which are sheets, and a separating part.
FIG. 10 of the accompanying drawings shows the construction of a conventional sheet feeding apparatus provided in such a document feeding apparatus, and in this sheet feeding apparatus, a pickup roller 73 for feeding documents S is held by the movable end portion of a pivotally supported pick up arm 71. The pickup arm 71 is pivotally supported with the drive shaft 71a of a separation roller 74 for separating the documents S fed by the pickup roller 73 one by one as a fulcrum. The separation roller 74 is in pressure contact with a separation pad 75, and this pressure contact part (nip part) constitutes a separating part for separating the sheets.
The reference numeral 70 designates a stopper member pivotally supported by the pickup arm 71, and this stopper member 70 is held in a state shown in the figure by its upper end abutting against the cover member 72 of the document feeding apparatus during standby. Design is made such that when the stopper member 70 is in such a state, the leading edge of the document S abuts against the stopper member 70 and does not enter the separating part.
When the document S is to be fed, the pickup arm 71 descends in the direction of arrow Y, whereby the pickup roller 73 held by the pickup arm 71 contacts with the document S and is rotated to thereby feed the document S. On the other hand, the abutment of the stopper member 70 against the cover member 72 is released in operative association with the descent of the pickup arm 71, and therewith, the stopper member 70 becomes pivotally movable in a counter-clockwise direction along a guide groove 76. Since the stopper member 70 is pivotally movable as described above, the stopper member 70 is pushed and pivotally moved by the leading edge of the document S fed by the pickup arm 71 and the document S enter the separating part. In this manner, the documents S are fed by the pickup roller 73, and are separated one by one by the separating part constituted by the separation roller 74 and the separation pad 75.
However, when in such a conventional sheet feeding apparatus, for example, the pickup arm 71 is not fixed, if the stopper member 70 is pressed in the direction of arrow Z by the documents when the documents are set in the standby state shown in the figure, the upper surface of the stopper member 70 will come to press the cover member 72.
When the stopper member 70 thus presses the cover member 72, the pickup arm 71, which is not fixed, is depressed in the direction of arrow Y and as a result, there has occurred the inconvenience that the stopper member 70 is released.
In order to prevent such an inconvenience, in case that the pickup arm 71 is designed not to be vertically moved when, for example, the documents S are set, the driving construction of the pickup arm 71 has become complicated and this has led to an increase in cost. Also, there have been many limitations for applying such a construction.
So, the present invention has been made in view of such present situation and has as its object to provide a sheet feeding apparatus and an image scanning apparatus in which a stopper member can be operated simply and at a low cost and reliably and an image forming apparatus provided with the image scanning apparatus.
The present invention provides a sheet feeding apparatus for feeding sheets supported on sheet supporting means by sheet feeding means, and separating and feeding the fed sheets one by one by separating means, the sheet feeding apparatus being provided with holding means for moving the sheet feeding means between a sheet feeding position wherein the sheet feeding means abuts against the sheets supported on the sheet supporting means and a standby position wherein the sheet feeding means is spaced apart from the sheets, and stopper means for abutting against the leading edges of the sheet supported on the sheet supporting means, and blocking the entry of the sheets into the separating means, wherein when the holding means is moved to make the sheet feeding means abut against the sheets supported on the sheet supporting means, the stopper means is pressed and moved by the holding means, and after the stopper means has been moved by the holding means, the stopper means is pressed and further moved by the sheets fed by the sheet feeding means to thereby make the passage of the sheets possible.
The present invention also provides a sheet feeding apparatus for feeding sheets placed on a sheet stacking tray by a pickup roller, and separating and feeding the fed sheets one by one by a separation roller and a separation pad, the sheet feeding apparatus being provided with a pickup arm on which the pickup roller is mounted and which is moved between a sheet feeding position wherein the pickup roller abuts against the sheets supported on the sheet stacking tray and a standby position wherein the pickup roller is spaced apart from the sheets, and a stopper for abutting against the leading edges of the sheets supported on the sheet stacking tray to block the entry of the sheets into the separation pad, the stopper being provided with an abutting portion against which the leading edges of the sheets supported on the sheet stacking tray abut, and a pressing portion abutting against the pickup arm, wherein when the pickup arm is moved for the pickup roller to feed the sheets, the pressing portion is pressed by the pickup arm and the stopper is moved and further, the sheet fed by the pickup roller moves the stopper to thereby make the passage of the sheet possible between the pickup arm and the pressing portion.